Telephony.



No. 747,491. PATENTED DEC. 22, 1,1903.`

H. 0. RUGH. TELEPHONY. APPLIOTIOI FILED JUNE 3, 3.902.

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f n Hauff DLFILLQ B- m ,my-un" H rmegs No. 747,491. y Patented December 22, 1903;

UNITED STATES.. PATENT OFFICE.

HARRY O. RUGH, OE CHICAGO, ILLINOIS, ASSIGNOR TO ILLINOIS ELECTRIC SPECIALTY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONY.

SPECIFICATION formingpart of Letters Patent N o. 747,491, dated December` 22, 1903.

Applioationiled June 2,1902. Serial No. 109.840. (No model.,

To all whom t may concern.- ing compensation for variation in the resist- Be it known that I, HARRY O. RUGH, a citiances of the metallic sides of the circuit that zen of the United States, residing at Chicago,` is designed to complete both telephonie cirin the county of Cook and State of Illinois, cuits. In the preferred embodiment of the 55 5 have invented a certain new and useful Iminvention I employ a rheostat included in provement in Telephony, of whichthe followloop-circuit with the said metallic circuit to ing is'a full, clear, concise, and exact descripinclude more resistance in one side and exv tion, reference being had to the accompanyclude resistance from the other side, as occaing drawing, forming a part of this specitision may require. 6o 1o cation. Where the invention is applied to trunk- My invention relates to telephony, and has lines forming links in the double telephonie for its object the provision of means to secure circuits, each trunk-line is preferably properfect transmission of voice-currents simulvided with a rheostat at each end thereof to taneously between four subscribers over a be Within the control of the operators, these 65 x 5 talking-circuit including two metallic sides. rheostats being included in loop or closed cir- A system of telephony to which my invencuit with the trunk-line, which trunk-line is tion is applicable embodies metallic sides of inductively related through the agency of rea circuit adapted for interposition between peating-coils with the metallic telephonesubscribers in communication and a groundlines that are to be united thereby and pref- 7o zo ed talking-circuit interposed between other verably in conductive relation withthe groundsubscribers in conversation, this grounded ed-circuit telephone-lines that are also to be circuit including portions of the sides of the united thereby, the arms of the rheostats metallic circuit in multiple. A well-known preferably constituting terminals of conducinstance ot' such a system as generally de-i tors that are or are adapted to be the oiice- 75 z5 scribed above is one employing trunk-lines terminals of the grounded telephone-lines.

between exchanges, the trunklines being In the preferred embodiment of the invenpreferably in the form of closed metallic cirtion the arms of the rheostats terminate in cuits in inductive relation with the telephonetrunk-line springs with which plugs of cordlines or continuations of the telephone-lines circuits are adapted for engagement to eect 8o 3o that they unite. The terminals of the trunkcomplete connection between the grounded lines at the exchanges are associated with substations. switching appliances and cord connecting I will explain my invention more fully by apparatus adapted for connecting groundreferenceto the accompanyingdrawing,which ed telephone-lines therewith, the metallicillustrates two metallic-circuit telephone- 85 35 sided trunk-line being adapted for inclusion linesl and two grounded circuit telephonein circuit with the grounded telephone-lines, lines, together with some of the associated the sides of the trunk-.line being connected vcentral-office apparatus, these lines being in parallel in the grounded circuit. In this united for conversation through the agency manner the double conversation may be carof atrunk-line associated with rheostats, con- 9o 4o ried 'onby way of the single trunk-line cirstituting in its association with the trunkcuit. line the preferred embodiment of my inven- Difticulty has been experienced hitherto in tion. connection with systems embodying the char- The apparatus at each of the snbstations acteristics above pointed out in that the re- 90 120A and B is well understood by those 9r 45 sistances of the metallic sides of the trunkskilled in the art, there being shown at each line are likely to be thrown out of equality, of these substations a telephone switch-hook thereupon giving rise to cross-talk between 1, a telephone-receiver 2, a transmitter 3, the the two telephonic circuits formed in part primary and secondary windings of an inducthereby, which circuits obviously should be tion-coil l, a call-bell 5,and a hand-operated roo 5c telephonically distinct. magneto-generator 6, whereby signals may My invention consists in means for eectbe sent and received and conversation carricd on when connections have been properly established. The substations 90 and 120 have their lines terminating at the exchanges C and D, there being provided a spring-jack 7 for each of these telephone-lines, or in the event of a multiple switchboard it is obvious that the number of jacks .may be multiplied.

In the embodiment of the invention shown a trunk-line 8 extends between the exchanges C and D, terminating in resistances 9 and 10. In the form of the invention shown the sides of the trunk-line form,with the resistances 9 and 10, a closed circuit, there being contained inthe trunk-line repeating-coils l1 and 12, whereby the trunk-line is inductively related with coils 13 13, terminating in the trunk-line jacks 14 and 15 at the exchanges C and D. There is provided at each of the exchanges C and D usual cord connecting apparatus, including plugs 16 and 17, and as such cord connecting apparatus forms no especial part of my present invention a detailed description thereof will not be essential, as various elements entering into this apparatus are clearly illustrated diagrammatically.

When the metallic lines extending to the stations 90 and 120 are united for conversation as indicated in the drawing, telephonic currents arising in one line will by induction be set up in the trunk-line circuit and from this circuit be propagated to the other line. In order that the same trunk-line circuit eX- tending between the exchanges may also serve to unite grounded lines, the trunk-line jacks 18 and 19 at the stations C and D may terminate in rheostat-arms 20 and 21, which by having metallic connection with the resistances 9 and 10 serve to connect the trunkline jacks through both sides of the trunkline, which are included in parallel, as will be apparent. The grounded telephone-lines extending from stations A and B may terminate in the spring-jacks 22 and 23 and there may be employed the usual cord connecting apparatus 24 and 25 for connecting the jacks 18 22 and 23 25. If the vresistancesin the sides of the trunkline are exactly in balance, then voice-currents may be propagated over the trunk-line circuit between the two sets of telephone-lines Without interference or crosstalk. If, however, the resistances are out of balance, as very frequently occurs, even after most carefuladjustmentand sometimes daily, then there will be interference and cross-talk, which by means of my invention I obviate, the most effective means being the employment of the resistances 9 and 10 in association with the rheostat-arms 2O and 21, which rheostatarms obviously may be so adjusted as to compensate for variation in resistance between the sides of the trunk-line to render these resistances exactly equivalent, and thereby prevent cross-talk.

It is obvious that changes may readily be made in the system of my invention shown without departing from the spirit of the inlimited to the precise arrangement illustrated; but,

Having thus described my invention, I claim as new and desire to secure by Letters Patentl. In a telephone system, the combination with a metallic circuit employed in uniting telephone-substations for conversation, of grounded telephone-lines including the sides of the said circuit in parallel, and means at each exchange end of said circuit controlled by the respective exchange-operator for compensating for` difference in resistance between the sides of the said metallic circuit, whereby to prevent cross-talk, substantially as described.

2. In a telephone system, the combination with a metallic circuit employed in uniting telephone-substations for conversation, of grounded telephone-lines including the sides of the said circuit in parallel, and an adjusting resistance included in the metallic circuit at each exchange end thereof and controlled by the respective exchange-operator for compensating for difference in resistance between its sides, whereby to prevent crosstalk, substantially as described.

3. In a telephone system, the combination with metallic-circuit telephone-lines extending from substations to an exchange, of a double-sided trunk-line for uniting the subscribers lines, grounded-circuit telephonelines having included in their circuit the sides of the trunk-line in parallel, and means at each end of the trunk-circuit and controlled by the respective operator for compensating for diierence in resistance between the sides ofthe trunk-line, whereby to prevent cross-talk, substantially as described.

4f. In a telephone system, the combination with metallic-circuit telephone-lines extending from substations to an exchange, of a double-sided trunk-line for uniting the subscribers lines, grounded-circuit telephonelines having included in their circuit the sides of the trunk-line in parallel, and an adjusting resistance included in the trunkline circuit at each exchange end thereof and controlled by the respective exchangeoperator for compensating for dilerence in resistance between the sides of the trunkline, to prevent cross-talk, substantially as described.

5. In a telephone system, the combination with metallic-circuit telephone-lines extending from substations to anexchange, of a double-sided trunk-line for uniting the subscribers lines, grounded-circuit telephone-` lines having included in their circuit the sides of the trunk-line in parallel, means at each exchange end of said trunk-line and controlled by the respective exchange-operator for compensating for difference in resistance between the sides of the trunk-line, to prevent cross-talk, and a repeating-coil inductively associating the trunk-line with the vention, and I do not, therefore, Wish to be telephone-line, substantially as described.

IOO

` 6. In a telephone system, the combination with metallic-circuit telephone-lines extending from substations to an exchange, of a double-sided trunk-line for uniting the subscribers lines, grounded-circuit telephonelines having included in their circuit the sides of the trunk-line in parallel, an adjusting resistance included in the trunk-line circuit at each exchange end thereof and controllable by the respective exchange-operator for compensating fordierence in resistance between the sides of the trunk-line, to prevent .cross-talk between the metallic circuit and the grounded circuit, and a repeating-coil inductively associating Vthe trunkline with the telephone-line, substantially as described.

7. In a telephone system, the combination with metallic-circuit telephone-lines extending from substations to an exchange, of a double-sided trunk-line for uniting the subscribers lines, grounded-circuit telephonelines having included in their circuit the sides of the trunk-line in parallel, means at each exchange end of the trunk-line and controlled by the respective exchange-operator for compensating for difference in resistance between the sides of the trunk-line, to prevent cross-talk, and two repeating-coils, one at each end of the trunk-line circuit, for inductively associating the trunk-line with the subscribers lines, substantially as described.

8. In a telephone system, the combination with metallic-circuit telephone-lines extending from substations to an exchange, of a double-sided trunk-line for uniting the subscribers lines, grounded-circuit telephonelines having included in theircircuvit the sides of the trunk-line in parallel, an adjusting resistance included in the trunk-line circuit at each exchange end thereof and controlled by the respective exchange-operator for compensatin g for dierence in resistance between the sides of the trunk-line, to prevent crosstalk between the metallic circuit and the grounded circuit, and two repeating-coils, one at each end of the trunk-line circuit, for inductively associating the trunk-line with the subscribers lines, substantially as described.

In witness whereofI hereunto subscribe my name this 29th day of May, A. 'D. 1902.'

. HARRY O. RUGH. Witnesses:

LYNN A. WILLIAMS, HARVEY L. HANsoN. 

